Given the success and the potential of such a propagation model to explain many of the timing properties of black hole X-ray binaries, there have been attempts to integrate the basic idea of the model with one which can also explain the time averaged spectrum and other timing features such as Quasi-periodic Oscillations (QPOs). A popular model to explain the hard X-ray emission from these sources during the hard spectral state, is that the standard accretion disc is truncated and the inner region is a hot flow [1]}, [2]}. For such an accretion disc geometry, there have been a series of works [3]}, [4]}, [5]}, [6]}, which incorporate the basic effects of stochastic propagation model. Such an integrated approach, can explain the time-averaged spectra and the temporal properties such as rms-flux and time-lags arising due to propagation. The model can also explain the \(\sim 1\)  Hz QPO observed in these sources as relativistic precession of the hot flow. There is no doubt that in the future, there will be more such attempts to provide a comprehensive picture using more complex accretion geometries with the propagation model being an integral part of such an approach.
